Vibrations in motorcycles contribute to rider fatigue. In an attempt to address this problem, some manufacturers have used softer springs or more-compliant shock absorbers. However, what may be appropriate for one rider weighing, say, 120 pounds, might be inappropriate for another rider weighing, say, 300 pounds .
The principal source of such vibrations is, of course, the engine itself and irregularities in the road. Various vibratory forces are transmitted from the road through the tires and suspension to the motorcycle frame. While some riders clamor for a smooth ride, other riders want a stiff ride, and still others want a combination of the two.
At least one manufacturer, Harley-Davidson, manufactures a motorcycle having a two-piece articulated frame. This bike, known as a "Softail", has a main frame part, and a rearward frame part pivotally connected to the main frame. The rearward part carries the rear wheel. A shock absorber and spring are operatively arranged between the frame parts to reduce the transmission of vibratory forces from the rear wheel to the main frame. However, this design has a non-cushioned pivotal joint between the two frame sections. Hence, vibrations may still be transmitted from the rear wheel through this joint to the main frame.
It would be desirable to provide an improved articulated motorcycle frame that would damp vibrations transmitted to the main frame, and reduce the vibrations felt in the main frame that are attributable to the engine.